Year	mmol per litre
1980	4.914
1981	4.913
1982	4.912
1983	4.906
1984	4.902
1985	4.9
1986	4.898
1987	4.899
1988	4.892
1989	4.877
1990	4.861
1991	4.844
1992	4.83
1993	4.815
1994	4.806
1995	4.799
1996	4.79
1997	4.782
1998	4.771
1999	4.762
2000	4.751
2001	4.739
2002	4.729
2003	4.717
2004	4.705
2005	4.692
2006	4.681
2007	4.672
2008	4.667